1. Field of the Invention
The present invention relates to a hardware-efficient demodulator, and more particularly, to a hardware-efficient demodulator for a CDMA adaptive antenna array mechanism in a mobile radio communication system.
2. Description of the Related Art
A CDMA system does not require a specific reference signal necessary to apply an adaptive antenna array to the system, differently from a TDMA system since the CDMA system utilizes a code sequence. Thus the CDMA system is basically suitable to a use of an antenna array.
The TDMA systems mainly employ algorithms using a spatial reference signal such as MUSIC, since the number of interference signals are small and power quantity of each interference signal is large therein. But, the CDMA system can not use such algorithms as MUSIC having a limitation in a nulling performance of the interference signal, since there exist a plural number of interference signals having a small power quantity of an interference therein, the limitation being caused according to the number of array-antenna elements.
Since the existing CDMA mobile radio communication systems generally combine only information provided in a temporal region by using a rake receiver, information of a spatial region can not be utilized. And, problems are caused in aspects of coverage, system capacity and transmission capability of high-rate data.
Further, the CDMA system mainly had an application of an algorithm considering the code sequence as the reference signal, but it was not especially done some endeavor for minimizing a size of a hardware and maximizing its performance improvement, maintaining a systematic merit of the existing and embodied CDMA system as it is. Besides, in a case of a blind algorithm which does not have a necessity for a specific reference signal and directly computes beamforming weight vectors without a prediction for a direction of an arrival(DOA), there are many cases as a convergence problem.
A CDMA system not having a use of the adaptive antenna array, generally combines only information provided in a temporal region through a rake receiver, then uses it. Meantime, a CDMA system using the antenna array can simultaneously utilize not only information of the temporal region but also information of a spatial region, accordingly it is needed a demodulator based on an efficient hardware structure capable of using such information.